Thanks Hong for presenting the case of a middle-aged woman with recent diagnosis of Grave’s disease off methimazole who presented with A fib with RVR and congestive heart failure, raising a debate on thyroid storm!

Clinical Pearls:

• Thyroid storm is an extremely rare (1 in 500,000) but life-threatening diagnosis (up to 30% mortality) that should not be missed.
• Degree of thyroid hormone elevation or TSH suppression is not a criteria for diagnosing thyroid storm! In fact, levels are typically similar to those of patients with uncomplicated thyrotoxicosis.
• Common clinical feature is cardiovascular symptoms (heart failure, arrhythmia, tachycardia) but more specific finding is AMS.
• Scoring criteria to screen for thyroid storm include Burch/Wartofsky and the Akamizu criteria, but they have not been validated.
• Consult endocrine early if you suspect thyroid storm!

Thyroid storm: 

Risk factors:

• Longstanding untreated hyperthyroidism
• Precipitants:
  • Thyroid/non-thyroidal surgery
  • Trauma
  • Infection
  • Acute iodine load
  • Parturition
  • Irregular use or discontinuation of antithyroid treatment

Etiology: not clearly understood, but possibly related to the following

• Rapid rate of increase in thyroid hormone levels?
• Increased responsiveness to catecholamines?
• Enhanced cellular responses to thyroid hormone?
• The degree of thyroid hormone elevation or TSH suppression is not typically more profound than uncomplicated thyrotoxicosis

Clinical features:

• CV (>60% of cases)
  • Tachycardia
  • CHF
  • Arrhythmias
• Hyperpyrexia
• AMS (considered by many to be essential to diagnosis)
  • Agitation, anxiety, delirium, psychosis, stupor, coma
• Features associated with worse outcomes?
  • AMS
  • Older age >60
  • Mechanical ventilation
  • Not using antithyroid drugs or beta blockers

Diagnosis: 

• Clinical! No universally accepted criteria or validated clinical tools.  Degree of hyperthyroidism is not a criterion for diagnosis.  Some to know of that might be helpful:
  • Burch and Wartofsky (sensitive, not specific)
    • > 45: highly suggestive of thyroid storm
    • 25 – 44: impending storm
    • <25: thyroid storm unlikely
  • Akamizu (Japanese) system developed in 2012 (less sensitive but more specific)

Treatment

• ICU admission!
• Regimen
  • Beta blockers ⇒ control symptoms from increased adrenergic tone
  • Thionamide ⇒ block new hormone synthesis. PTU is preferred because it blocks peripheral conversion of T4 to T3.
  • Iodine solution ⇒ block release of thyroid hormone (saturated solution of potassium iodide)
  • Iodinated radiocontrast agent (not available anymore in most places) ⇒  inhibit peripheral conversion of T4 to T3
  • Glucocorticoids ⇒ reduce T4 to T3 conversion, promote vasomotor stability, and treat any associated relative adrenal insufficiency
  • Bile acid sequestrants ⇒ decrease enterohepatic recycling of thyroid hormones (only in very severe cases)
• Principles
  • Start with beta blockers + PTU, and stress dose steroids
  • 1 hour later: start SSKI q6h (after hormone synthesis has been halted with PTU, otherwise SSKI can make thyroid storm worse)